Heritage homes in the Christchurch residential red zone could be rescued from demolition.

The red zone is home to dozens of 19th-century homes, including a cluster of historic cottages in the Avon Loop, and tells the history of suburban Christchurch.

The New Zealand Historic Places Trust (NZHPT) is combing the red zone for heritage buildings and is in talks with authorities and landowners to save some of them.

The heritage watchdog aims to save a Kinsey Tce cabin in Sumner that was built for Captain Robert Scott's 1910-12 Antarctic expedition.

NZHPT acting general manager Ann Neill said the trust was searching for historic homes in the red zone.

''We are researching the residential red zones, but generally on a site-by-site basis. We've conducted a historic survey on a couple of areas, but this is really just to ascertain the presence of standing pre-1900 structures or areas of pre-1900 occupation,'' she said.

Neill said the trust would approach the Christchurch City Council and the Canterbury Earthquake Recovery Authority (Cera) about saving some historic properties in the red zone.

''NZHPT will be following up with the council, Cera and the owners to discuss possible options, which may include relocation,'' she said.

The Kinsey Tce cabin was initially sent to the Antarctic as a meteorological hut but was not used and was sent back to Christchurch in 1912.

It eventually found a home in expedition agent Sir Joseph Kinsey's garden.

The land was red-zoned in June and the owners approached the trust about possible relocation.

''NZHPT is working with the Antarctic Heritage Trust, Antarctica New Zealand and others to find a secure interim site and funding for relocation to enable this cabin to be retained as an important link to the 1912 Terra Nova expedition and its vital connection to Christchurch,'' Neill said.

Neill said early research showed ''there is reasonable heritage potential in the cabin''.

''On the face of it, the building meets our criteria for having historical and social significance or value,'' she said.

''It may well hold technological significance, though we cannot say this for certain without further detailed research, which could be conducted at a later time.''

There are only two buildings in the residential red zone that were protected in the council's city plan.

One is a 1870s home in River Rd in Richmond, which could be the oldest house in the red zone.

The other is an Orion electricity substation in Retreat Rd in Avonside dating from about 1927.

The owner of the River Rd property said the building could not be saved, but the substation was relatively unharmed in the Canterbury earthquakes.

Orion quake-strengthened its network in the 1990s and only four of its 314 substations were badly damaged in the quakes.

An Orion spokeswoman said no decision had been made on the future of the substation, which provides power to remaining red-zone residents and is part of a network that allows power to be rerouted if another substation fails.

The two buildings are no longer protected under the city plan as it is superseded by the Canterbury Earthquake Recovery Act.